Combined pressure and temperature control for steam heating systems



July 28, 1936. F. c. BRODERICK 2,049,288

COMBINED PRESSURE AND TEMPERATURE CONTROL FOR STEAM HEATING SYSTEMS Filed Marbh 20, 1955 no u Luvs 1 17 5 /29 Jflz/erzi'ar .Fredem'ak Cf Broderz'ok Patented July 28, 1936 UNITED STATES COMBINED PRESSURE AND TEMPERATURE CONTROL FOR STEAM HEATING SYS- TEMS Frederick o. Broderick, Winnetka, in.

Application March 20, 1935, Serial No. 12,003

6 Claims.

This invention relates to control devices for low pressure steam or vapor heating systems and particularly to such devices designed to control operation of the combustion apparatus in acpressure conditions. v

The main objects of this invention are to provide a unitary control device for regulating the will primarily control a combustion device in accordance with predetermined boiler conditions regardless of the demand of a coacting room 20 thermostat; to provide such a device arranged to stop operation of a combustion device in response to apredetermined maximum steam pressure and start operation of the combustion device only in response to a predetermined minimum 25 water temperature; and to provide such a device having an independent temperature responsive element and a pressure responsive element dependent on the temperature responsive element.

30 A specific embodiment of this invention is shown in the accompanying drawin in which:

Figure 1 is a View showing the relationshipof the switching elements of a control device when in their normal operating position.

Fig. 2 is a view showing the same when actuated by means responsive to a predetermined maximum pressure.

Fig. 3 is a view of the same showing the elements when actuated thermostatically in re- 40 sponse to a predetermined minimum water temperature.

Fig. 4 is a sectional view of the control device in elevation showing the mounting of the switching elements. v

5 Fig. 5 is a fragmentary sectional detail showing an arrangement of pressure responsive means for actuating one of the control device switching elements. I

Fig. 6 is a diagrammatic layout showing the 50 circuit connections between the control device and associated apparatus for complete summer and. winter control of a low pressure steam or vapor heating system.

Fig. 7 is a view illustrating the manner in which 1 55 the control device is associated with a boiler.

cordance with predetermined temperature and As shown in the drawing the control device comprises an independent switching element arranged to be directly actuated in response to temperature changes and a second switching element arranged to be actuated by a pressure re- 5 sponsive means upon the occurrence of a predetermined maximum pressure only, which second element is dependent upon the first'elem-ent for being reset to its normal operating position; the first switching element serving the function 10 of starting or stopping a combustion device directly in accordance with predetermined thermostatic conditions, and the second switching element serving the function of stopping the combustion device only upon the occurrence of a predetermined maximum pressure condition.

In the form shown in the drawing the control device comprises a. single throw mercury tube switching element'l, mounted on an arm 2 which in turn is carried at the end of a rotatable rod or 2 shaft 3.

The rotatable rod or shaft 3 extends through and projects outwardly from the rear wall of a casing 4 and is journaled in a carrier member 5 which in turn is shiftably mounted on the inner side of the rear wall of thecasing 4.

Surrounding the outwardly projecting portion of the rod 3 is a helical thermostatic spring ele ment 6, one end of which is fastened to the rod 3 as at l and the other end of which is secured to the carrier member 5, and housing the thermostatic element 6 and the outwardly projecting portion of the rod 3 is a tubular shell 8 which is closed at its outer end and which at its inner end is threaded into an internally threaded collar or nipple 9 formed on the outside of the rear wall of the casing 4.

The carrier member 5 is provided with a lever ID by means of which it may be rotatably shifted on the axis of the rod 3 and the carrier member is 40 so mounted on the inner side of the casing 4 that it may be shifted only by the lever l0 and will remain relatively fixed against any turning action that might be exerted by the thermostatic spring element 6. The lever ll) extends through the casing 4 and serves as an indicator and adjusting means for varying the temperature ranges within which the device is intended to function. e

As shown inthe drawing the arm 2 extends upwardly from the axis of the rod 3 and engages a second arm I I which is pivotally hung from a post l2 on the inner side of the.casing 4, and which carries a second mercury tube switching element l3. As shown the arm 2 is provided with a pin or lug l4 which extends into a slot I5 formed in the lower portion of the arm II, and the slot I5 is so formed that when the arm II is in its normal operating position as shown in Fig. 1, the arm 2 may swing freely to a limited extent in either direction about the axis of the rod 3 without effecting movement of the arm Thus the arm II is also free to be shifted to a limited extent without eifecting movement of the arm 2, as indicated in Fig. 2. 7

However, should the arm ll be shifted in one direction, shifting of the arm- 2 in the opposite direction will cau the arm II to be returned to its normal vertical position due to engagement r,

of the pin or lug M with the end of the slot I5.

As shown in Fig. 5, the pressure responsive means for actuating the arm I I may comprise, a piston l6 which is mounted in a cylinderv 'I'I secured on a wall of the'casing 4, the cylinder I! having a pipe connection I8 which communicates directly with the steam chamber of a boiler as shown in Fig. 7. Thus pressure generated within the boiler will by way of the pipe connection I8 act on the head IQ of the piston and cause the same to be shifted within the cylinder against the action of a spring 20. As indicated in Fig. 5, the pressure responsive means ispositioned so as to engage a flange formed on one side of the arm II and the arrangement is such that when the piston is in its normal position as shown in Fig. 5, the arm II will be in a substantially vertical position, the spring 20 being tensioned to normally hold the piston in its retracted position and to permit movement of the piston within the cylinder I! only in response to a predetermined pressure.

Thus the spring 20 will prevent movement of the piston I6 until a predetermined pressure is exerted on the piston head l9 at which time the piston will be projected outwardly from the cylinder I'I against the flange NJ and cause angular shifting of the arm II.

As shown in the drawing, each of the switching elements I and I3 comprises a tube containing a quantity of mercury. and having a plurality of contact members disposed in one end. The

tubes and I3 are positioned in the control device so that the contact members of one tube will be disposed on the opposite side of the arms 2 and l I from the contact members of the second tube. Also the switching elements I and I3 are so mounted on the arms 2 and II that when they are in their normal operating position, as shown in Figure 1 the tubes will be substantially parallel to each other and both'inclined downwardly in the same direction.

Thus in the normal operation position the mercury contained in one tube will surround the contact members thereof and the mercury contained in the other tube will rest at the opposite end of the tube from the end in whichits respective contact members are disposed.

In the arrangement shown in the drawing, the pressure responsive tube or mercury switching element I3 is inclined downwardly to the left which is the normal position for the tube l3 when ates the tube I is so arranged that upon a drop in temperature the tube I will be tilteddownwardly to the right which is thus the cold side 5 I of the tube I.

Thus upon drop in temperature and resultant tilting of the tube I to the right or cold side, the mercury contained in the tube I flows by gravity. to the lower end thereof and surrounds the contact members housed therein.

In the specific embodiment of this invention herein shown each mercury switch is provided with three spacing contact members disposed at one end for the reason that some control circuits are of the 'three wire type. However, it will be readily understood that circuits might be employed such that only two contact members would be required in each switching element.

As shown in Fig. 6 the control device is intended to'operate in conjunction with an independent thermostat switch or a room thermostat 2| located in the premises to be heated by the heating system and positioned so as to be affected by temperature variations in the said premises, and the'control device together with the room thermostat 2| serves to control the operation of a combustion device 22 through a relay 23.

The circuit shown is of the type commonly known as a low voltage circuit, since onlylow voltage current provided by a choke coil included in the relay 23 is supplied to the control device or the'room thermostat 2|.

In such a circuit current is initially supplied by a 110 volt line comprising the leads 24 and 25 which are respectively connected to opposite ends of the primary 26 of the choke coil 21.

One side of the secondary 28 of the choke coil is connected by means of a lead 29 with one contact 30 of the room thermostat 2|. The other side of the'secondary 28 is connected to one end of a relay actuating coil 3|. The opposite end of the coil 3|.is connected to a maintaining switch 32 by means of a lead 33 and by means of a lead 34 to the contact member 35 of the tube 3.

The maintaining switch 32 is generally included in all low voltage or three-wire control devices or circuits. However in the circuit shown in Fig. 6 it serves no operative function and will not be further referred to since in practice it, together with all leads connected thereto, might be omitted without interfering with the operation of the circuit as herein intended. The ground terminal 36 of the thermostat 2| is connected by means of lead 31 to the contact 38 in the tube 3. Thus, through the thermostat 2| and the tube I3 a closed circuit may be obtained which would energize the relay coil 3| and cause the switch 39 to be closed so as to close a circuit between the lead 40 which is connected to the power line lead 25 and the combustion 7 device 22, the opposite side of the combustion device being connected by lead 4| with the power line lead 24.

The thermostatically operated mercury switch serves merely the purpose of shunting the-ther- 5 mostat 2| by short-clrcuiting the lines 29 and 34 through the terminals 42 and 43 and their respective leads 44 and 45.

In operation the control device is mounted on a steam boiler, as shown in Fig.7, with the thermostatic element extending through the boiler wall and'into the water chamber at a convenient point below but adjacent the boiler water line. The pressure tube I8 is then connected in any 75 suitable manner with the boiler steam chamber so that any pressure produced therein will be transmitted by the connection l8 to the cylinder I! of the pressure switch actuating device.

Under normal conditions the mercury switches of the control device assume the position shown in Fig. 1, the thermostatic element 3 being so tensioned through manipulation of the adjusting lever Ill that at the desired mean boiler water temperature, for example 200 F., the mercury switch I will be in the normal position shown. Under such conditions the contacts 35 and 38 of the mercury switch l3 will be surrounded by mercury and a circuit between them will be closed. The switch I3 is so arranged that, it will be held in its normal position as shown in Fig. 1

' by the eccentric weight of the mercury in the lefthand side of the tube, which will cause the arm thereof to rest against the retarded plunger l6 of the pressure actuated mechanism. It will also be observed that under such condition the circuit between the contacts 42 and 43 of the tube is open. Thus upon closing of the contact 30 of the room thermostat 2|, current will fiow from the choke coil 28 through the lead 29 and thence through the thermostat 2| and the lead 31 to the switch IS. The switch 43 being normally closed, a circuit will be completed between the contacts 38 and 35 and the current will thus flow through the lead 34 to the relay coil 3| and thencebackto the secondary 28 of the choke coil. Thus the relay coil 3| will be actuated and the switch 39 closed to complete the power circuit to the combustion device 22. a

The combustion device will now operate to supply heat to the boiler and generate steam therein, until the steam pressure in the space above the boiler water line indicated by the numeral 46 in Fig. '7 reaches a predetermined maximum point, at which time the steam pressure, being transmitted to the pressure responsive element of the control device by way of the pipe connection l8, will cause movement of the piston |9 against the action of the spring 20 and thus shift the arm of the swtich |3 to the position shown in Fig. 2,

causing the switch 3 to tilt downwardly on the high side and break the circuit between the contacts 35 and 38 which will cause the switch 39 of the relay to be released and open the power circuit to the combustion device 22, causing the same to stopits operation.

Under ordinary conditions the temperature of the boiler water will not go much beyond 212 F. during the generation of steam, and thus the thermostatic actuation of the switch I will merely cause the same to tip further to the left or hot side and because of the shape of the aperture l in which the pin l4 moves, movement of the arm 2 to the left or hot side will not interfere with the pressure operated movement of the arm H and the mercury tube l3.

Under these conditions the mercury held in the tube |3 will, due to its weight, hold the switch in the boiler water has cooled to a predeterminedminimum, for example 185? to190 F., at which time thermostatic actuating mechanism of the switch I will cause the same to tilt to the right or cold side as shown in Fig. 3, which movement will by way of arm 2 cause a shifting of the arm back to its normal position wherein the mercury switch l3 will be tilted to the left or low side, again closing the circuit between the con-- tacts 35 and 38 so that if the room thermostat 2| is not yet satisfied, the combustion device 22 will again start operation and continue to generate 5 steam until the thermostat 2| is satisfied, or until the steam pressure again reaches the predetermined maximum point.

However, should the thermostat 2| have become satisfied before the boilerwater has cooled to the predetermined minimum temperature, the relay operating circuit will be opened at the thermo-' stat 2| until the minimum boiler water temperature is reached and then be closed by means of the mercury tube I, which, when tilted to the cold side as shown in Fig. 3, completes a circuit between the contacts 42 and 43, shunting or shortcircuiting the thermostat 2| and thus causing operation of the combustion device until the boiler water temperature has reached its maximum point (200 F.). At this point the switch I will be shifted by the thermostatic element 6 until it assumes the position shown in Fig. 1 where it is tilted to the hot side so that the circuit between the contacts 42 and 43 is open, allowing the combustion device to stop operation.

Thus in winter operation of the heating system the boiler water temperature will be maintained at a substantially constant point, whether or not the room thermostat is calling for heat. However on a demand for heat'steam will be generated for distribution to the premises heating interchangers or radiators until the maximum predetermined pressure has been reached, at which point the combustion apparatus will be shut-down and the steam that has been generated will continue to circulate through the radiators.

As the steam is condensed a reduction of pressure will take place within the steam chamber of the boiler and a slight vacuum will ultimately be produced. Such reduction of pressure will cause the latent heat within the boiler water to produce an additional quantity of steam which will tend to supply heat to the premises until the boiler water has cooled to the point where tilting of the mercury switch I again closes the circuit to the relay 23 to start the combustion device. In this manner'with a minimum operation of the combustion device a maximum amount of heat is distributed to the premises heating devices or radiators.

In summer operation, when it is desired to maintain the temperature of the boiler water within a predetermined range for the purpose of heating water for domestic use, the control of the combustion apparatus will be entirely through the thermostatically actuated .mercury switch l, which will operate in the usual manner of boiler thermostats to start the combustion device when the boiler water'temperature drops to a predetermined minimum point and stop the combustion device when the temperature reaches a predetermined maximum point. The maximum point being lower than that at which steam will be generated obviates the possibility of heat being transmitted from the boiler to the premises heating radiators when it is not desired or when there is no demand on the part of the room thermostat 2|.

The main advantages of my improved control 7 device lie in the fact that frequent starting and stopping of the combustion device is eliminated and the fact that the heating system may be operated the year around for heating water for domestic use under the control of the same conentirely independent of any thermostatic control,

there is frequent starting and stopping of the combustion device because of rapid fluctuations in steam pressure. This is particularly objectionable in low pressure steam installations where a maximum pressure of approximately 8 ounces is used. Here the pressure drop is so rapid that the combustion device is operated at frequent short intervals. Such operation is ineificient due to waste of fuel upon starting of the burner and due to the large amount of electric current that is necessary on starting the burner motor.

My improved device completely overcomes.

these objections and promotes greater efilciency in the operation of the entire heating system.

In the drawing herein the combustion device is indicated as being a burner motor. However, it will be understood that any of various electrically actuated combustion devices may I" used, such as an oil valve; a gas valve, a stoker motor, damper regulator, etc.

Although but one specific embodiment of this invention has been herein shown and described, it will be understood that details of the construction shown may be altered or omitted without departing from the spirit of this invention as defined by the following claims.

I claim:

1.. A control device comprising a switching means, a thermostatic element arranged to actuate said switching means, a second v switching means, a pressure responsive means arranged to actuate said second switching means, and means mechanically interconnecting said switching means with each other and arranged whereby actuation of said second switching means in one direction is independent of the first switching means and actuation in the opposite direction is dependent upon actuation of said first switching means.

2. In an electric control device, the combination with a thermostatically actuated switching means and a pressure actuated switching means of means mechanically connecting said switching means with each other arranged to permit independent operation of said thermostatically actuated switching means to open and close an electric circuit and to permit independent operation of said pressure actuated switching means to open an electric circuit only.

3. In an electric control device the combination with switching means arranged to open and close two independent circuits, of pressure actuated means arranged to operatesaid switching means to open one circuit only, and thermostatically actuated means arranged to operate said 10 switching means to open and close the other of said circuits and to close the first circuit.

4. An electric control device comprising switching means arranged to open and close two independent circuits each controlling a common electrlcally operated device, an independent thermostatic switch connected serially in one of said circuits, pressure responsive means arranged to operate said switching means to open said one circuit only, independent of said thermostat, and other thermostatically actuated means arranged to operate said switching means to open and close the other of said circuits and to close'the first circuit.

5. A control system for steam boilers comprising a switch and a room thermostat connected in series to electrically control a combustion device, a pressure responsive means actuated by steam pressure arranged to open said switch only; a second switch arranged to control said combustion device independently of the first switch and said thermostat, thermostatically actuated means responsive to boiler water temperatures arranged to open and colse said second switch, and means actuated by said second switch arranged to close the first switch only.

6. A control device comprising a pivotally mounted mercury switch arranged to normally close an electric circuit, pressure responsive means arranged to shift said switch to open'said 40 electric circuit only, a second pivotally mounted mercury switch arranged to open and close a second electric circuit, thermostatically actuated means arranged to shift said second switch to open and close said second circuit in response to predetermined temperature changes, and means actuated by said thermostatic means arranged to shift the first switch and close its respective circuit when said second switch is actuated to close said second circuit, said last named means being arranged to permit independent operation of said second switch.

FREDERICK c. BRODERICK. 

